This invention relates to ion exchange chromatography which employs the single-column method. The "single-column method" does not signify that only one separation column exists in a liquid chromatographic analyzer, but it signifies that the separation of components for one sample is executed with one separation column. Accordingly, a case where a plurality of samples are subjected to the separations of components by a plurality of corresponding separation columns in parallel is also covered within the category of the single-column method.
In the past, in separating the constituents of a mixed amino acid sample by the liquid chromatography which exploited an ion exchange resin, individual separation columns for acidic and neutral components and for basic components were used. This method was disadvantageous in that, since the sample needed to be divided in two and then introduced into the two separation columns, the precious sample was wasted.
In 1972, J. R. Benson published that 17 components of amino acids constituting protein were separated by a separation column (American Laboratory: volume 10, page 53). Thereafter, an amino acid analyzer which separates 47 components of amino acids in an organism liquid in 5.5 hours by employing the single-column method has come into the market. In this analyzer, during the analytical cycle of one sample, 5 sorts of elutes of different compositions are successively supplied in change-over.
In the above method for separating the 47 components of the amino acids of the organism liquid, it takes about 160 minutes to separate acidic amino acids and neutral amino acids which total 30 components, and it takes about 170 minutes to subsequently separate basic amino acids which total 17 components. Although this method has shortened the analytical time considerably as compared with the past method, the development of a speedier method of analysis has been desired.